Added todo note about IsFinished bug.
Merge pull request #5 from behindcurtain3/master

Cleaning up the PrevGameTime assignment
Update GAME.md
Cleaned up usings in Interfaces
Moved PropertyBag from Interfaces to GameObjects namespace
Moved Bridges and Items layer above Cliff layer
Refactored Heros Update routine.
Changed storage structure of PostGameShaders to Dictionaries in
TeeEngine
Re-introduced Light Shader in Hero
Added support for specifing LightSources from .tmx files.
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-BasicLightSource is now LightSource
-LightSource is now an Entity that implements ISizedEntity
-LightSource now registers itself to a LightShader on PostInitialize
hook